<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        li{
            width: 80px;
            height: 40px;
            background-color: lightgreen;
            color: red;
            float: left;
            /*该变列表前面的符号标志*/
            list-style-type: none;
            text-align: center;
            line-height: 40px;
        }
        li:hover{
            width: 80px;
            height: 40px;
            color: blue;
            background-color: bisque;
            /*鼠标手型设定*/
            cursor:pointer;
        }
        li:hover div{
            /*消失的div再现*/
            display: block;
            width: 80px;
            height: 40px;
            color: chartreuse;
            background-color: bisque;

        }
        /*div消失*/
       div{
           display: none;
       }
    </style>
</head>
<body>
   <ul>
       <li>首页
          <div>博客</div>
           <div>相册</div>
           <div>帮助</div>
       </li>
       <li>博客
           <div>博客</div>
           <div>相册</div>
           <div>帮助</div>
       </li>
       <li>相册</li>
       <li>帮助</li>
       <li>关于</li>
   </ul>
</body>
</html>